1. Field of the Invention
This invention relates to hard, gas permeable, biomedical devices including contact lenses prepared from monomeric polysiloxanes polymerized with a modulus modifier and a tear film stabilizer.
2. Prior Art Statement
U.S. Pat. No. 3,808,178 discloses contact lenses fabricated from a copolymer of a polysiloxanylalkyl acrylic ester and an alkyl acrylic ester. The copolymer is said to have increased oxygen permeability. Wettability can be imparted to the copolymer by the addition of about 0.1 to about 10 percent by weight of one or more hydrophilic monomers such as hydroxyalkyl acrylates and methacrylates, acrylic and methacrylic acid, acrylamide, glycidyl acrylate and N-vinyl pyrrolidinone.
U.S. Pat. No. 4,136,250 teaches, in part, a water absorbing polysiloxane which may be used to make soft contact lenses. The polymer is obtained by copolymerizing a siloxane monomer with a variety of hydrophilic monomers, e.g., acrylic acid or a mixture of hydrophilic and hydrophobic monomers, styrene can be included in the mixture. The siloxane monomers can be reduced to a formula similar to but yet critically different from the instant polyorganosiloxane monomers. From U.S. Pat. No. 4,136,250 the following siloxane monomer may be derived: ##STR1##
In the formula the oxygen atom with the arrow pointing to it is present in the '250 formula but not present in the instant polyorganosiloxane monomers of this invention. This oxygen atom, because of its placement between the silicone and carbon atoms, is subject to hydrolysis and alcoholysis. Stability is important if this material is to be used for biomedical devices, such as contact lenses, since these types of devices are usually heated in the presence of water in order to disinfect them. If, during heating the contact lens loses its shape, then it loses its optics. This means that the material taught in '250 would be undesirable for use in certain medical devices including contact lenses.
U.S. Pat. No. 4,152,508 discloses hard contact lenses having a high oxygen permeability. The lens material is a copolymer of a siloxanylalkyl ester monomer, and itaconate ester and an ester of acrylic or methacrylic acid. Representatives of itaconate esters include phenyl itaconate, diphenyl itaconate and methyl phenyl itaconate.
U.S. Pat. No. 4,153,641 discloses contact lenses made from polymers and copolymers comprising poly(organosiloxane) polymers and copolymers formed by polymerizing a poly(organosiloxane) monomer .alpha.,.omega. terminally bonded through divalent hydrocarbon groups to polymerized, free radical polymerizably activated, unsaturated groups forming a polymer in a crosslinked network. Additionally, specific comonomers are disclosed which include lower esters of acrylic and methacrylic acids, styryls (including vinyl ethyl benzene and styrene) and N-vinyl pyrrolidinone which may be copolymerized with the above described poly(organosiloxane) monomer to form a copolymer. The instant invention preferred polysiloxane monomers include these poly(organosiloxane) monomers.
U.S. Pat. No. 4,189,546 discloses shaped articles for biomedical uses other than contact lenses made from polymers and copolymrs comprising poly(organosiloxane) polymers and copolymers formed by polymerizing a poly(organosiloxane) monomer .alpha.,.omega. terminally bonded through divalent hydrocarbon groups to polymerized, free radical polymerizably activated, unsaturated groups forming a polymer in a crosslinked network. Additionally, specific comonomers are disclosed which include lower esters of acrylic and methacrylic acids, styryls (including tertiary-butyl styrene and propyl styrene) and N-vinyl pyrrolidinone which may be copolymerized with the above described poly(organosiloxane) monomer to form a copolymer. The instant invention preferred polysiloxane monomers include these same poly(organosiloxane) monomers.
U.S. Pat. No. 4,208,506 discloses soft contact lenses made from polymers and copolymers comprising polyparaffinsiloxane polymers and copolymers formed by polymerizing a polyparaffinsiloxane monomer .alpha.,.omega. terminally bonded through divalent hydrocarbon groups to polymerized, free radical polymerizably activated, unsaturated groups forming a polymer in a crosslinked network. Additionally, specific comonomers are disclosed which include lower esters of acrylic and methacrylic acid, styryls and N-vinyl pyrrolidinone which may be copolymerized with the above described polyparaffinsiloxane monomer to form a copolymer. The instant invention preferred polysiloxane monomers include the same polyparaffinsiloxane monomers.
U.S. Pat. No. 4,228,269 discloses contact lenses and blanks for same are made by polymerizing at least one styrene type monomer, optionally with at least one crosslinking monomer and optionally with other monoolefinically unsaturated monomers. Preferably the styrene monomer is a styrene substituted in the ring by at least one alkyl group, e.g., tertiary-butyl styrene and/or isopropyl styrene. The lenses have high gas permeability.
U.K. patent application No. 2,036,765 discloses soft contact lenses comprised of a hydrated copolymer of a major proportion of an hydroxyalkyl acrylate or methacrylate, up to 12% by weight of any ethylenically unsaturated acid or anhydride, a major proportion of a crosslinking monomer and a minor proportion of styrene or substituted styrene, the free acid or anhydride groups being in bulk form. The reinforcing effect of the styrene in the copolymer can be increased by incorporating it in more concentrated sequence, e.g., as a block copolymer.
U.S. Pat. No. 4,243,790 discloses gas permeable contact lenses made from a copolymer of styrene and acrylate ester or hydroxy acrylate ester with optionally up to about 10% methacrylic acid. A preferred soft lens composition is 20% to 30% styrene, 2% to 3% methacrylic acid, 1% crosslinking agent and the balance acrylate material. With styrene percentages of 40% to 80%, methacrylic acid should not be added as poor optical properties may result.
U.S. Pat. No. 4,277,595, granted on application Ser. No. 074,944 by William G. Deichert et al, discloses monomeric polysiloxanes endcapped with activated unsaturated groups polymerized with acrylic acid to form a soft contact lens. The acrylic acid is present in an amount from about 5 to 30 weight percent of the total polymer. These instant polysiloxane copolymer soft contact lenses have unexpectedly high water absorption and are hydrophilic.
U.S. Pat. No. 4,276,402, granted on application Ser. No. 075,365 by Richard E. Chromecek et al, discloses monomeric polysiloxanes endcapped with activated unsaturated groups polymerized with acrylic acid and polycyclic ester of acrylic acid or methacrylic acid to form a soft contact lens. The polycyclic monomer is present in an amount from about 5 to 50 weight percent of the total polymer and the acrylic acid is present in an amount from 1 to about 30 weight percent. These terpolymer soft contact lenses have unexpectedly high tensile strengths and improved tear strengths as compared to copolymers of polysiloxane and acrylic acid.